1. Field of the Invention
The invention relates to a magnetic resonance spectroscopy method in which a first magnetic rf field having the Larmor frequency of carbon is generated in order to suppress the doublet structure of at least one CH group in compounds containing carbon and hydrogen, after which a second magnetic rf field having the Larmor frequency of the hydrogen in the relevant CH groups is applied to the examination zone and the spin resonance signal formed is detected. The invention also relates to a device for performing the method.
2. Description of the Related Art
In the spectroscopic examination of compounds containing carbon and hydrogen the carbon spectra (of the 13 C isotope) exhibit vigorous structures which are due to the J couplings of the carbon atoms to the hydrogen nuclei. Depending on the orientation of the nuclear spins of the hydrogen atoms coupled to the carbon atoms, the magnetic field at the area of the relevant carbon atom will be larger or smaller resulting in different Larmor frequencies of a plurality of closely neighbouring lines (multiplet) in the spectrum.
It is inter alia known from U.S. Pat. No. 4,470,014 that this multiplet structure can be reduced by applying a magnetic rf field having the Larmor frequency of hydrogen during the detection of the spin resonance signal whose frequency corresponds to the Larmor frequency of carbon. This rf field continuously flips the nuclear spins of the hydrogen atoms coupled to the carbon atoms to and fro during the measurement of the spin resonance signals, so that on average in time they no longer influence the carbon atoms. This method is referred to as "decoupling" and the spectra thus formed are referred to as decoupled spectra.
However, it is imperative that the rf magnetic field influences the hydrogen nuclei, i.e. the protons, to a substantially higher degree than the J coupling. When the CH group whose multiplet structure is to be suppressed exhibits a strong J coupling, very strong rf magnetic fields are required so that the associated rf load precludes the use of such methods for in vivo examinations.